Comparison of two species of Notopterygium by high-performance liquid chromatography-photodiode array detection-electrospray ionization tandem mass spectrometry.

Notopterygium incisum Ting ex H.T. Chang (N. incisum) and Notopterygium forbesii Boiss (N. forbesii) are two medicinal species of Qianghuo (a well-known traditional herbal medicine in China) that are widely used in clinical prescriptions for the treatment of colds and rheumatism. To compare the chemical constituents of these two plant materials, the phenolic constituents and coumarins of these two species were comprehensively and systematically analyzed by high-performance liquid chromatography-photodiode array detection-electrospray ionization tandem mass spectrometry (HPLC/DAD/ESI-MS(n)) for the first time. A total of 25 compounds (nine phenolic compounds and 16 coumarins) were detected in the methanol extracts. These compounds were separated on a C18 column and identified or tentatively characterized on the basis of their UV spectra and MS fragmentation behavior. In contrast to previous reports, we found that these two plant species possess very different coumarin patterns. O-Demethylfuropinnarin (18), phenethylferulate (19), notopterol (20), and isoimperatorin (22) were the predominant constituents of N. incisum, whereas nodakenin (6), 6-O-trans-feruloylnodakenin (12), p-hydroxypenethylanisate (16) and isoimperatorin (22) were the major constituents of N. forbesii. O-Demethylfuropinnarin (18), phenethylferulate (19) and notopterol (20) were only detected in N. incisum and can be regarded as useful taxonomic markers for differentiating these two plant species. Considering the marked differences in the main chemical constituents of N. incisum and N. forbesii, the biological activities of these two species should be further investigated and compared to ensure consistency and efficacy in the pharmaceutical applications of these materials.

Differentiation of four pairs of furocoumarin isomers by electrospray ionization tandem mass spectrometry.

A mass spectrometric method based on the combined use of electrospray ionization, collision-induced dissociation (CID) and ion-trap time-of-flight (IT-ToF) tandem mass spectrometry was used to identify four pairs of furocoumarin isomers. Our results show some characteristic mass spectrometric differences in isomeric furocoumarins. In the MS(2) spectra, the relative abundance ratios of m/z 131 [M + H - 2CO](+) to m/z 143 [M + H - CO(2)](+) and m/z 115 [M + H - CO-CO(2)](+) of psoralen are less than one, but both ratios are greater than one in the case of isopsoralen. The relative abundance of m/z 159 [M + H - CO(2)](+) is much higher than that of m/z 175 [M + H - CO](+) in the case of bergaptol, but this trend is reversed in xanthotoxol. Moreover, three diagnostic ions of m/z 189 [M + H - CO](+), m/z 185 [M + H - CH4O](+) and m/z 161 [M + H - 2CO](+) are observed in the MS(2) spectrum of xanthotoxin but not in that of bergapten. Further, two diagnostic ions of m/z 226 [M - H - CH(3) - CO](-) and m/z 210 [M - H - CH(3) - CO(2)](-) are observed in the MS(2) spectrum of isoimperatorin but not in that of imperatorin. The relative abundance of product ions associated with some diagnostic ions can be used to characterize furocoumarin isomers.